The present invention relates generally to the field of machinery seals or machinery packing and more particular annular fluid sealing members and more specifically improvements to the "U-type" composite packing ring seal.
Annular ring type seals are commonly used in the industry for sealing various applications such as valve stems, gas lift valves and the like. These seals can be used in either a static or dynamic situation for the prevention of leaking between parts. U-type seals are generally a composite construction including an outer U-shaped body with an inner flexible or pliable member which occupies the inside of the U. The sides of the U are referred to as lips. U-type seals are typically assembled with an interference and are force fit with dimensions between the sealing lips being important especially when dealing with joint packing applications of high pressure or where one part moves with respect to the other, such as for example in the application of a high pressure valve. In that regard, the valve stem would be the part surrounded by the annular U-type seal. The interference or force type fit of the sealing lips provides for a good seal against the valve stem for example, and the seal itself allows the stem to turn with respect to the other parts of the valve such as the valve body. This is of course is only exemplary of the uses of such annular U-type seal rings.
U-type seals are found in the prior art. Seals of this general type can be seen for example in U.S. Pat. No. 4,174,846 entitled "Sealing Ring" and issued to Lynn Scott. Various other U-type seals have been patented including for example, U.S. Pat. No. 3,342,500 issued to Knudson, U.S. Pat. No. 3,653,672 issued to Felt, U.S. Pat. No. 4,328,972 issued to Albertson, et al. and U.S. Pat. No. 3,851,888 issued to Limpson. These are exemplary of this type of annular seal. A discussion of various other seals which are pertinent to the present invention follows herein.
U.S. Pat. No. 4,428,590 issued on Jan. 31, 1984 to Aaron J. Pippert and H. T. Miser entitled "Anti-Extrosion Sealing Device With Hinge-Like Bridge Section" discloses a seal and method of making same wherein a first body is formed with a plurality of parallel, spaced apart bores therethrough. A second body is molded onto the first body so that it fills the bores and forms enlarged portions adjacent the ends of the bores, whereby the two bodies are permanently mechanically interlocked. The Pippert, et al. device differs from the present invention because of the difficulty of manufacturing the elastomer portion of the device. The present invention uses a simple O-ring elastomer which pre-loads the lips of a U-cup body.
U.S. Pat. No. 4,328,972 issued on May 11, 1982 to Kenneth R. Albertson and Ralph Peterson entitled "Seal Ring and Method of Manufacture" is a sealing ring having a U-shaped shell member and an actuator member formed in situ from liquid elastomer. The shell member has a base portion with two legs extending from the base to form a cavity therebetween which is filled with a liquid elastomer and cured in situ. This device thus has an elastomer that is cured in place unlike the present invention which uses a pre-cured, pre-formed elastomer to pre-load the lips.
U.S. Pat. No. 4,232,873 issued on Nov. 11, 1980 to Jules M. Hock entitled "Ring Spring For Composite Machinery Seals and Method of Manufacturing Same" reveals an elastomeric resilient ring spring for use in an annular elastomeric boot generally of a U-cup configuration having an exposed annular groove which is generally x-shaped, the ring spring being generally +-shaped including four lobes, first and second opposed lobes extending parallel to the plane of the ring spring and third and fourth opposed lobes extending perpendicular to the plane of the ring spring. The dimensions of the ring spring are approximately the same as those of the groove whereby rotation of the ring spring about its ring axis through an angle of 45.degree. permits mating of the ring spring into the groove in the boot.
Dennis H. Iverson issued U.S. Pat. No. 4,193,606 on Mar. 18, 1980 entitled "Machinery Seal" illustrates a U-cup type machinery seal for circumferential placement about a rotating and/or reciprocating member. The seal includes a boot having a generally triangular cross-section in the groove for biasing radially positioned lips into sealing engagement with the machinery to be sealed. The triangular cross section of the groove differs from the oblong groove of the present invention that is occupied by an expander of greater diameter than the width of the groove to pre-load the lips of the seal body.
U.S. Pat. No. 4,174,846 entitled "Sealing Ring" issued to Lynn S. Scott on Nov. 20, 1979 communicates an annular sealing ring comprises a U-cup having a pair of lips for forming a cavity therebetween and elastomeric expander ring mounted within the cavity. Sealing edges on the lips are contacted by members to be sealed and are positioned on the outside of the lips at a vertical location at or below the horizontal center line of the expander ring is mounted within the cavity. The Scott U.S. Pat. No. 4,174,846 patent uses an outer surface of the lips which is squared rather than the round expander end portion of the present invention in combination with rounded lips. With the present invention, this provides a generally rounded surface to one end of the seal which makes the seal easier to install in a cavity. Unless seal alignment is very close, in fact, installation is difficult on the Scott type seal.
Lynn S. Scott also was issued U.S. Pat. No. 4,013,299 entitled "Sealing Ring" on Mar. 22, 1977 dealing with an annular sealing ring that comprises a U-cup having a pair of lips for forming a cavity therebetween and an elastomeric expander ring mounted within the cavity. Sealing edges on the lips are contacted by members to be sealed and are positioned on the outside of the lips at a vertical location at or below the horizontal center line of the expander ring when the expander ring is mounted within the cavity. The Scott U.S. Pat. No. 4,013,299 patent does not provide for lip loading in the are a of the O-ring. Further, the heel or base portion configuration does not allow loading directly on an expander with the configuration shown.
On May 27, 1975, U.S. Pat. No. 3,885,801 entitled "Packing" was issued to John B. Scannell. The Scannell U.S. Pat. No. 3,885,801 patent discloses a sealing assembly for sealing in two directions, comprising an elastomeric seal ring with a pair of lips, a solid elastomeric loading ring between the lips, and a pressure inverting pedestal ring active on the loading ring such that when fluid pressure is behind the pedestal ring the fluid pressure bypasses the pedestal ring and acts on the loading ring to deform the same to press the lips into sealing engagement with the members, and when fluid pressure is behind the seal ring the latter pushes the loading ring against the pedestal ring to likewise cause the loading ring to deform and press the lips into sealing engagement with the members.
The Scannell patent uses an end portion which is not rounded as is the case with the present invention, but rather shows a squared configuration which is difficult to install and which requires a mating surface having multiple curves as shown in FIGS. 4 and 5 of the drawing.
Alma A. Limpson, Jr., et al. was issued U.S. Pat. No. 3,851,888 on Dec. 4, 1974 entitled "Machinery Seal", which teaches that a U-cup type of machinery seal adapted to be disposed in an annular configuration about moving member such as a rotating or reciprocating shaft, or a reciprocating piston, and includes an annular groove adapted to receive an elastomeric spring to bias the seal, said annular groove defining a pair of axially extending leg portions and a base portion joining said leg portions, the width of the base being less than the width of the machinery portion within which it is to be restrained, each of said leg portions having end surfaces which are sloped with respect to the side surfaces of said base portion to provide tips which extend radially inwardly and outwardly, respectively with a total radial width between the tips which is greater than the radial width of the machinery confinement in which the seal is to be constrained. The annular groove has a transverse cross-section similar to the four-lobed, substantially flattened X-shaped cross-section of the elastomeric ring spring, the minimum internal radial cross-sectional width of said annular groove being located at least as close to the axially outward opening of said groove as said radially extending tips are, thereby to apply mechanical wedging and hydrostatic pressure from said ring seal directly to said tips. The base surface of said being substantially planar permits multiple usage thereof in a stacked configuration or in single usage, without altering the seal characteristics of the said base surface.
On Nov. 19, 1974, Charles L. Tanner was issued U.S. Pat. No. 3,848,880 for "Fluid Seal" disclosing herein is a fluid pressure seal useful over a wide range of fluid pressures. The seal is adapted for use between two either relatively moving or static members one of which has an annular sealing groove formed in the surface thereof adjacent the other member. A continuous annular boot fabricated from a relatively hard material and of generally U shape in cross section is positionable in the sealing groove with its body portion adjacent the low pressure side of the groove and a pair of generally parallel spaced leg portions positionable respectively adjacent the base of the groove and the other member with little or no initial interference. A second coaxial continuous annular ring fabricated from a resilient flowable material, such as rubber, has a first body portion positioned between the legs of the boot and a second body portion extending beyond the boot legs in the high fluid pressure direction. The second body portion has a width dimension in its free state greater than the distance between the boot legs and is adapted to be in a state of compression after installation in the sealing groove to effect a seal at low fluid pressure.
Maurice F. Felt, was issued U.S. Pat. No. 3,653,672 on Apr. 4, 1972 entitled "Seal Ring" which teaches a seal ring is provided having rounded lips wherein the top point of sealing is below the top of the ring and the ring has a large area in contact with the sealing surface. The seal ring may have a hollow center portion or a filter strip may be employed in the center of the ring. The filter strip, if used, is of rectangular configuration.
U.S. Pat. No. 3,342,500 issued on Sept. 19, 1967 to C. B. Knudson for "Packing Construction" relates to machinery packing, and more particularly to the new and improved composite packing ring structure for effective hydrostatic loading of the packing may be accomplished so that stresses, element distortions and other deleterious features are eliminated in the packing when the same is loaded in the machinery for which it is intended. A further object was to provide an composite O-ring packing ring member wherein suitable relief area is provided the O-ring in such a manner that distortion or cutting into the O-ring by the packing ring member is least likely to take place. Also to provide annular relief areas in the packing ring member of a snap-seated composite packing ring construction wherein suitable relief ares are provided for O-ring expansion when the packing ring is disposed under pressure; and also to provide a composite packing construction which is self-loading type having suitable means for accommodating distortion in the packing ring when the same is installed and loaded in the machinery. It is an overall composite of various types of composite rings for relief of interference in its fit.
U.S. Pat. No. 3,279,805 issued on Oct. 18, 1966 to Henry J. Quinson entitled "Sealing Joint" teaches of sealings joints composed of two rings or washers arranged concentrically, their respective diameters being such that a spaces exists between the two rings, this space being filled out with a packing made of rubber or of a similar material which is in intimate contact with the corresponding faces of the rings, the height of said packing being slightly greater than that of the rings so that the packing overlaps each place surface of the rings.
Maurice D. Felt was also issued a U.S. Pat. No. 3,169,776 on Feb. 16, 1965 for "Multiple Purpose Self-Loading Machinery Packing" disclosing packing rings for machinery to effect sealing and, more particularly, to a ne and improved packing structure which can be used in U-cup and V-packing contexts to great advantage both in sealing performance qualities obtained and in reduction in manufacturing costs. It is primarily intended for use in packing rings, piston rings and gland structures in industrial equipment such pumps and compressors.
U.S. Pat. No. 3,132,869 issued on May 12, 1964 to Rodney R. Campbell, Assignor and Malcolm R. Mahen, Trustee entitled "Fluid Pressure Responsive Seal Assembly" illustrating annular fluid seals interposed between relatively movable members having a clearance therebetween and in which there may be at times substantial fluid pressure differential across the seal. It is particularly useful when employed in a fluid valve adapted to open and close a fluid line carrying high pressures.
On Aug. 28, 1956, U.S. Pat. No. 2,760,794 was issued to William Hartranft for "Vibration Rings For Mechanical Seals" divulging improvements in rings which are sometimes called "vibration rings" employed to resiliently support an abutment ring which is employed with or as a part of a mechanical sealing device for sealing a space between a shaft and a machine-casing opening through which the shaft extends.
The above discussed prior art U-cup type machinery seals with elastomeric expanders generally are force fit into a packing gland with the amount of interference between the gland width and the seal lips being 15% to 25% of the gland width. This high interference of the seal lips causes difficulty when forcing the seal into the packing gland. The present invention provides a design that can utilize a lessor interference fit between the gland width and the seal lips of 7% to 12% which provides an effective seal at high and low pressures and is easier to force into the packing gland. Further, the U-cup type seals with elastomeric expanders of the prior art usually have a beveled or square outer free end that is difficult to force into the seal gland. The present invention utilizes an outer arcuate curved surface that is easier to force into the packing gland. Further, U-cup type seals in the prior art usually have a heel or base portion that is squared or square with an arcuate concave surface. When these prior art seal configurations are used in a stacked configuration the upper seal packing ring loads directly upon the lower packing ring without interaction on the expander. The present invention utilizes an arcuate curved heel (or base portion) that interacts directly upon the expander which causes an inward and an outward force on the lateral projections which results in a more effective seal.
Typical uses of the seal of the present invention are, for example, valve stem packing, gas lift valve packing, pump down plug packing, chemical injection valve packing, plunger pump packing, swivel joint packing, well head lubricator packing, hydraulic cylinder piston and rod packing, back pressure valve packing, downhole safety valve packing, well head tubing hanger packing, and intensifier packing.